Astronomers have found a new dwarf planet

Illustration
of the orbit of the new dwarf planet, RR245 (orange line).
Objects as bright or brighter than RR245 are
labeled.Alex
Parker/OSSOS team

Astronomers using the the Canada-France-Hawaii Telescope on the
dormant Mauna Kea volcano in Hawaii announced on
July 11, 2016 that they've discovered a new dwarf planet orbiting
beyond Neptune. The international team of astronomers said the
new object is roughly 435 miles (700 km) in size and has one of
the largest orbits known for a dwarf planet. The Minor Planet Center described the
object as the 18th largest in the Kuiper Beltand has designated it as
2015 RR245.

The new dwarf planet was found as part of the ongoing Outer Solar
System Origins Survey (OSSOS).

A dwarf planet is defined as an object in our solar system with a
mass in the range of planets or moons, at least massive enough
for the object's self-gravity to have crushed it into a ball
shape. Unlike moons, dwarf planets are in direct orbit
around our sun. Unlike the major planets of our solar system,
dwarf planets have not cleared their neighborhoods of the debris
in their own orbits, according to the 2006 IAU definition of
planets, the same definition that caused Pluto to lose its
major planet status.

The icy worlds beyond Neptune trace how the giant planets formed
and then moved out from the sun. They let us piece together the
history of our solar system. But almost all of these icy worlds
are painfully small and faint: it's really exciting to find one
that's large and bright enough that we can study it in detail.

How large is it? The size of RR245 is not yet exactly known,
because astronomers aren't sure yet what lies on its surface.
Bannister said:

There it was on the screen — this dot of light moving so slowly
that it had to be at least twice as far as Neptune from the sun.

The astronomers' statement said the team became even
more excited when they realized that the orbit of RR245 takes it
more than 120 times farther from the sun than Earth.

They said that — after being more than 8 billion miles (12
billion km) from the sun for hundreds of years — RR245 is now
traveling toward its closest approach at 3 billion miles (5
billion km). It'll reach this (extremely distant) closest point
around 2096.

RR245 has been observed for only one of the 700 years it takes to
orbit the sun. Where it came from, and how its orbit will slowly
evolve in the far future, is still unknown. As astronomers
observe it longer, they'll be able to define its orbit more
precisely. Eventually, they'll give the object a real name.

The New Horizons spacecraft — which visited dwarf planet Pluto
last July — showed that these little worlds so far from the sun
have exotic geology, pointed out these astronomers. No spacecraft
is headed toward RR245, nor is one likely to be in our lifetimes.

But — now that they know it's there — astronomers will be
watching it.

Bottom line: Astronomers have discovered a new and very distant
dwarf planet, labeled RR245.